Flexible display device

ABSTRACT

A display device includes a flexible substrate including a bending area corresponding to an area at which the display device is bent, and a first area and a second area which is spaced apart from the first area by the bending area, a display element unit disposed in the first area of the flexible substrate; and a buffer member disposed in the bending area of the flexible substrate. The buffer member in the bending area includes: a first buffer member having a first maximum thickness, and a second buffer member having a second maximum thickness which is smaller than the first maximum thickness. Among the first buffer member and the second member, the first buffer member disposed closer to the first area and the second member disposed closer to the second area.

This application claims priority to Korean Patent Application No.10-2018-0083080, filed on Jul. 17, 2018, and all the benefits accruingtherefrom under 35 U.S.C. § 119, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND 1. Field

The present disclosure relates to a flexible display device, and moreparticularly, to a flexible display device having a driving memberattached thereto.

2. Description of the Related Art

A flexible display device can be used not only in portable electronicdevices such as a mobile phone, a smartphone, a tablet personal computer(“PC”), a smart watch, a watch phone, a mobile communication terminal,an electronic notebook, an electronic book, a portable multimedia player(“PMP”), a navigation device, or an ultra-mobile PC (“UMPC”), but alsoin various other products such as a television (“TV”), a notebookcomputer, a monitor, a billboard, or an Internet-of-Things (“IoT”)device.

A flexible display device, which is a display device having a displayunit, signal wiring and the like formed on a flexible substrate, made ofa flexible material such as plastic, so as to be able to display animage even when bent like paper, has attracted attention as anext-generation display device.

The range of application of the flexible display device has diversifiedfrom a static computer monitor and a TV to a mobile personal portabledevice, and research has been conducted on a flexible display devicehaving a relatively large display area and a reduced volume and weight.

SUMMARY

Exemplary embodiments of the present disclosure provide a flexibledisplay device capable of preventing defects by reducing or effectivelypreventing a flexible substrate or signal wiring from cracking even whenbent.

However, exemplary embodiments of the present disclosure are notrestricted to those set forth herein. The above and other exemplaryembodiments of the present disclosure will become more apparent to oneof ordinary skill in the art to which the present disclosure pertains byreferencing the detailed description of the present disclosure givenbelow.

According to an exemplary embodiment of the present disclosure, there isprovided a display device including a flexible substrate including abending area corresponding to an area at which the display device isbent, and a first area and a second area which is spaced apart from thefirst area by the bending area; a display element unit which iscontrolled to display an image, the display element unit disposed on theflexible substrate in the first area of the flexible substrate; and abuffer member disposed on the flexible substrate in the bending area ofthe flexible substrate. The buffer member in the bending area includes:a first buffer member having a first maximum thickness, and a secondbuffer member having a second maximum thickness which is smaller thanthe first maximum thickness, and among the first buffer member and thesecond member, the first buffer member disposed closer to the first areaand the second member disposed closer to the second area.

In an exemplary embodiment, a display device may further include on asame side of the flexible substrate which is opposite to that on whichthe display element unit is disposed: a first supporting member coupledto the first area of the flexible substrate; and a second supportingmember coupled to the second area of the flexible substrate, a firstinner side of the first supporting member facing a second inner side ofthe second supporting member. The flexible substrate bent at the bendingarea may dispose along a thickness direction of the display device: thesecond supporting member overlapping the first supporting member, thefirst inner side of the first supporting member corresponding to aborder between the first area of the flexible substrate and the firstbuffer member, and the second inner side of the second supporting membercorresponding to a border between the second area of the flexiblesubstrate and the second buffer member.

In an exemplary embodiment, the first buffer member may be in contactwith the first inner side of the first supporting member, the secondbuffer member may be in contact with the second inner side of the secondsupporting member, and a thickness of a portion of the first buffermember which is directly adjacent to and in contact with the first innerside may be greater than a thickness of a portion of the second buffermember which is directly adjacent to and in contact with the secondinner side.

In an exemplary embodiment, the first supporting member, the firstbuffer member, the second buffer member, and the second supportingmember may include a same material and form one integral body with oneanother.

In an exemplary embodiment, the first and second buffer members mayfurther include a moisture permeation preventing material. In thebending area, the first buffer member may cover a portion of theflexible substrate directly adjacent to the first inner side of thefirst supporting member, and the second buffer member may cover aportion of the flexible substrate directly adjacent to the second innerside of the second supporting member.

In an exemplary embodiment, each of the first and second supportingmembers may be thicker than each of the first and second buffer members.

In an exemplary embodiment, the flexible substrate bent at the bendingarea may further dispose: the first buffer member at a bent end of thedisplay device, and a bottom surface of the first supporting memberfacing a top surface of the second supporting member along the thicknessdirection of the display device. The first buffer member may extend fromthe bent end of the display device to dispose a first extension memberthereof overlapping the bottom surface of the first supporting memberalong the thickness direction of the display device.

In an exemplary embodiment, the first maximum thickness of the firstbuffer member extending to define the first extension member may begreater than a thickness of the first supporting member.

In an exemplary embodiment, the flexible substrate bent at the bendingarea may further dispose the first extension member of the first buffermember further overlapping the second supporting member along thethickness direction of the display device.

In an exemplary embodiment, on a same side of the flexible substrate onwhich the display element unit is disposed, the display device mayfurther include a driving member which controls the display element unitto display the image, the driving member disposed in the second area ofthe flexible substrate; and a circuit board which provides a controlsignal to the driving member, the circuit board connected to theflexible substrate at the second area thereof to be spaced apart fromthe driving member in the second area.

In an exemplary embodiment, on a same side of the flexible substrate onwhich the display element unit is disposed, the display device mayfurther include a third buffer in the first and second areas of theflexible substrate, the third buffer member facing the first and secondbuffer members in the bending area of the flexible substrate.

In an exemplary embodiment, a thickness of the third buffer member maybe smaller than each of the first and second maximum thicknesses of thefirst and second buffer members, and a material of the third buffermember may differ from materials of the first and second buffer members.

In an exemplary embodiment, a display device includes a flexiblesubstrate including a bending area corresponding to an area at which thedisplay device is bent, and a first area and a second area which isspaced apart from the first area by the bending area; a display elementunit which is controlled to display an image, the display element unitdisposed on the flexible substrate in the first area of the flexiblesubstrate; a buffer member disposed on the flexible substrate in thebending area of the flexible substrate, the buffer member in the bendingarea including: a first buffer member having a first maximum thickness,and a second buffer member having a second maximum thickness which issmaller than the first maximum thickness, and among the first buffermember and the second member, the first buffer member disposed closer tothe first area and the second member disposed closer to the second area;and on a same side of the flexible substrate which is opposite to thaton which the display element unit is disposed: a first supporting membercoupled to the first area of the flexible substrate, the firstsupporting member including a first inner side closest to the bendingarea being curved to have a first curvature; and a second supportingmember coupled to the second area of the flexible substrate, the secondsupporting member including a second inner side closest to the bendingarea. The flexible substrate bent at the bending area disposes along athickness direction of the display device: the second supporting memberoverlapping the first supporting member, and the curved first inner sideof the first supporting member protruding toward the first buffermember.

In an exemplary embodiment, the first buffer member may be in contactwith the curved first inner side of the first supporting member, thesecond buffer member may be in contact with the second inner side of thesecond supporting member, and a thickness of a portion of the firstbuffer member which is directly adjacent to and in contact with thecurved first inner side may be greater than a thickness of a portion ofthe second buffer member which is directly adjacent to and in contactwith the second inner side.

In an exemplary embodiment, the first supporting member, the firstbuffer member, the second buffer member, and the second supportingmember may include a same material and form one integral body with oneanother.

In an exemplary embodiment, the first and second buffer members mayfurther include a moisture permeation preventing material. In thebending area, the first buffer member may cover a portion of theflexible substrate directly adjacent to the curved first inner side, andthe second buffer member may cover a portion of the flexible substratedirectly adjacent to the second inner side.

In an exemplary embodiment, each of the first and second supportingmembers may be thicker than each of the first and second buffer members.

In an exemplary embodiment, the flexible substrate bent at the bendingarea may further dispose: the first buffer member at a bent end of thedisplay device, and a bottom surface of the first supporting memberfacing a top surface of the second supporting member along the thicknessdirection of the display device. The first buffer member may extend fromthe bent end of the display device to dispose a first extension memberthereof overlapping both the bottom surface of the first supportingmember and the top surface of the second supporting member along thethickness direction of the display device, and the first maximumthickness of the first buffer member extending to define the firstextension member may be greater than a thickness of the first supportingmember.

In an exemplary embodiment, on a same side of the flexible substrate onwhich the display element unit is disposed, the display device mayfurther include a third buffer member in the first and second areas ofthe flexible substrate, the third buffer member facing the first andsecond buffer members in the bending area of the flexible substrate.

In an exemplary embodiment, a thickness of the third buffer member maybe smaller than each of the first and second maximum thicknesses of thefirst and second buffer members, and a material of the third buffermember may differ from materials of the first and second buffer members.

According to the aforementioned and other exemplary embodiments of thepresent disclosure, a flexible display device capable of reducing oreffectively preventing defects by reducing or effectively preventing aflexible substrate or signal wiring from cracking even when bent.

Other features and exemplary embodiments may be apparent from thefollowing detailed description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will become moreapparent by describing in detail exemplary embodiments thereof withreference to the attached drawings, in which:

FIG. 1 is a top plan view of an exemplary embodiment of a flexibledisplay device according to the present disclosure;

FIG. 2 is a cross-sectional view of an exemplary embodiment of theflexible display device of FIG. 1 in an unbent state;

FIG. 3 is a cross-sectional view an exemplary embodiment of the flexibledisplay device of FIG. 1 in a bent state;

FIG. 4 is a detailed cross-sectional view of the flexible display deviceof FIG. 3;

FIGS. 5A and 5B are cross-sectional views illustrating an exemplaryembodiment of a method of forming a buffer member in a bending area of aflexible display device according to the present disclosure;

FIG. 6 is a cross-sectional view of another exemplary embodiment of aflexible display device in a bent state according to the presentdisclosure;

FIG. 7 is a cross-sectional view of still another exemplary embodimentof a flexible display device in a bent state according to the presentdisclosure;

FIG. 8 is an enlarged cross-sectional view of the flexible displaydevice of FIG. 7;

FIG. 9 is a cross-sectional view of yet another exemplary embodiment ofa flexible display device in a bent state according to the presentdisclosure;

FIG. 10 is a cross-sectional view of yet another exemplary embodiment ofa flexible display device in a bent state according to the presentdisclosure; and

FIG. 11 is a cross-sectional view of yet another exemplary embodiment ofa flexible display device in a bent state according to the presentdisclosure.

DETAILED DESCRIPTION

The advantages and features of the invention and methods for achievingthe advantages and features will be apparent by referring to theembodiments to be described in detail with reference to the accompanyingdrawings. However, the invention is not limited to the embodimentsdisclosed hereinafter, but can be implemented in diverse forms. Thematters defined in the description, such as the detailed constructionand elements, are nothing but specific details provided to assist thoseof ordinary skill in the art in a comprehensive understanding of theinvention, and the invention is only defined within the scope of theappended claims. Like reference numerals refer to like elementsthroughout.

An element described as being related to another element such as being“on” another element or “located on” a different layer or a layer,includes both a case where an element is located directly on anotherelement or a layer with no intervening element or layer therebetween anda case where an element is located on another element via another layeror still another element. In contrast, an element described as being isrelated to another element such as being “directly on” another elementor “located directly on” a different layer or a layer, indicates a casewhere an element is located on another element or a layer with nointervening element or layer therebetween.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “At least one” is not to be construed as limiting “a” or“an.” “Or” means “and/or.” As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.It will be further understood that the terms “comprises” and/or“comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

For a flexible display device having a display unit, signal wiring andthe like formed on a flexible substrate, made of a flexible materialsuch as plastic, so as to be able to display an image even when bentlike paper, cracks may be generated in the flexible substrate and/or thesignal wiring for various reasons. Such cracks may undesirably causedefects in a flexible display device.

FIG. 1 is a top plan view of an exemplary embodiment of a flexibledisplay device according to the present disclosure, and FIG. 2 is across-sectional view of the flexible display device of FIG. 1 in anunbent or flat state. As an exemplary embodiment of being unbent orflat, the flexible display device and components thereof may be disposedextended in a single plane.

Referring to FIGS. 1 and 2, the flexible display device and componentsthereof may be disposed in a plane defined by two directions which crosseach other. In FIG. 1, the vertical direction may define a firstdirection while the horizontal direction may represent a seconddirection which crosses the first direction. In FIG. 2, the verticaldirection may define a third direction which crosses each of the firstand second directions, to represent a thickness direction of theflexible display device and the components thereof, while the horizontaldirection may define the first direction or the second direction. InFIG. 1, the thickness direction is defined into the page view.

Referring to FIGS. 1 and 2, a flexible display device 1 includes adisplay area DA in which an image is displayed and a non-display areaNDA which is disposed at the periphery of the display area DA. Theflexible display device 1 may have an overall rectangular shape withright-angled or rounded edges, such as at corners thereof in the topplan view. However, the shape of the display area DA is not particularlylimited, and the display rea DA may have a circular shape, an ellipticalshape, or various other shapes in the top plan view.

The non-display area NDA is disposed on the periphery of the displayarea DA. The non-display area NDA may be disposed adjacent to both ofopposing relatively short sides of the display area DA. Also, thenon-display area NDA may be disposed adjacent not only to both of theopposing relatively short sides, but also to both of opposing relativelylong sides of the display area DA, and may be disposed at all the sidesof the display area DA to surround the display area DA. That is, thenon-display area NDA adjacent to the display area DA may form theborders of the display area DA.

The flexible display device 1 may include a display panel DP, whichgenerates and displays an image such as with light, and a driving member200, which is attached to the display panel DP and forms pixel circuitryof the display panel DP. The display panel DP may define a displayscreen of the flexible display device 1. In an exemplary embodiment, anouter surface of the display panel DP may define the display screen ofthe flexible display device 1. The driving member 200 may include adriver integrated circuit (“IC”).

The display panel DP may include components or devices (not illustrated)which are controlled or driven to generate and/or display an image.These components or devices may be disposed in the display area DA. Acontrol or driving signal may be applied to these components or devicesto generate and/or display the image at the display area DA.

In an exemplary embodiment, for example, an organic light-emitting diode(“OLED”) display panel may be used as the display panel DP. In thedescription that follows, it is assumed that the display panel DP is anOLED display panel, but the present disclosure is not limited thereto.That is, various other display panels such as a liquid crystal display(“LCD”) panel, a field emission display (“FED”) panel, or anelectrophoretic display panel may be used as the display panel DP.

In an exemplary embodiment, the display panel DP may include a main areaMA and a bending area BA at which the display panel DP and componentsthereof may be bent from a flat state thereof. The main area MA may beflat. In the main area MA, the display area DA and a part of thenon-display area NDA may be disposed. It will be understood that as usedherein related to bending, a reference to “display panel DP” alsoapplies to the components of the display panel DP.

The bending area BA may be disposed on at least one side of the mainarea MA. FIGS. 1 and 2 illustrate that there is provided one bendingarea BA near the lower side of the main area MA in the top plan view.Alternatively, the bending area BA may be disposed near the left, rightor upper side of the main area MA in the top plan view. Stillalternatively, the bending area BA may be disposed near two or moresides of the main area MA.

The display panel DP at the bending area BA may be bent in an oppositedirection to a display direction. As illustrated in FIG. 2, the displaydirection is indicated downward as ‘light direction’ in a case where theflexible display device 1 is of a top emission type. In an exemplaryembodiment, the non-display area NDA may partially overlap with the mainarea MA in a thickness direction of the flexible display device 1. Bybending at least part of the display panel DP in the non-display areaNDA in the opposite direction to the display direction, the bezel of theflexible display device 1 can be reduced when the display panel DP isbent.

The display panel DP may further include a sub-area SA extending fromthe bending area BA. The main area MA, the bending area BA and thesub-area SA may together define a whole planar area of the display panelDP. When the display panel DP is bent, a plane in which the sub-area SAis disposed may be parallel to a plane in which the main area MA isdisposed. When the display panel DP is bent, the sub-area SA may overlapwith the main area MA in the thickness direction. In an exemplaryembodiment, when the display panel DP is bent, the entire sub-area SAmay overlap with the main area MA in the thickness direction. Thebending area BA and the sub-area SA may both be included into thenon-display area NDA, but the present disclosure is not limited thereto.

The display panel DP may include a pad area disposed in the non-displayarea NDA. The pad area may be disposed in the sub-area SA, but thepresent disclosure is not limited thereto. Alternatively, the pad areamay be disposed in the main area MA or the bending area BA.

The pad area may include a plurality of pad terminals (not illustrated)through which a control or driving signal is provided to the displaypanel DP from outside thereof. The pad terminals may be connected tosignal wiring 150 extending from the display area DA and into thenon-display area NDA. The signal wiring 150 may be connected to thecomponents or devices of the display panel DP described above. Thedriving member 200 may be attached to the pad terminals. The control ordriving signal may be provided through the driving member 200 to thedisplay panel DP from outside thereof. In FIG. 1, the driving member 200may be considered as corresponding to the pad area without being limitedthereto.

The flexible display device 1 may further include a printed circuitboard PCB. The printed circuit board PCB may be attached to a part ofthe non-display area NDA on the outside of the pad area. That is, thepad area to which the driving member 200 is attached may be disposedbetween the display area DA and the area to which the printed circuitboard PCB is attached. The printed circuit board PCB may be attached toa lower part of the sub-area SA. The printed circuit board PCB may be aflexible printed circuit board, but the present disclosure is notlimited thereto. The printed circuit board PCB may be connected to thedisplay panel DP via a flexible film.

The flexible display device 1 may include the display panel DP, a backplate (310 and 320), and a buffer member (350 and 360).

The display panel DP may include a flexible substrate 110, which isdisposed across the entirety of the display panel DP, a pixel arraylayer 120 which is disposed on the flexible substrate 110 in the mainarea MA, and a thin encapsulation layer 130 having a relatively smallthickness. The display panel DP may further include the driving member200, which is disposed on the flexible substrate 110 in the sub-area SA.

The flexible substrate 110 may be a substrate for supporting variouselements of the display panel DP and/or the flexible display device 1.The flexible substrate 110 may be disposed across the main area MA, thebending area BA, and the sub-area SA and may be understood as includingareas respectively corresponding to those of the main area MA, thebending area BA and the sub-area SA.

The flexible substrate 110 may include or be formed of a soft material.In an exemplary embodiment, for example, the flexible substrate 110 maybe a film including one or more material selected from a polyesterpolymer, a silicone polymer, an acrylic polymer, a polyolefin polymer,and a copolymer thereof. Specifically, the flexible substrate 110 mayinclude one or more material selected from polyethylene terephthalate(“PET”), polybutylene terephthalate (“PBT”), polysilane, polysiloxane,polysilazane, polycarbosilane, polyacrylate, polymethacrylate,polymethylacrylate, polyethylacrylate, polyethylmethacrylate, acyclic-olefin copolymer (“COC”), a cyclic-olefin polymer (“COP”),polyethylene (“PE”), polypropylene (“PP”), polyimide (“PI”), polymethylmethacrylate (“PMMA”), polystyrene (“PS”), polyacetal (“POM”),polyetheretherketone (“PEEK”), polyester sulfone (“PES”),polytetrafluoroethylene (“PTFE”), polyvinyl chloride (“PVC”),polycarbonate (“PC”), polyvinylidene fluoride (“PVDF”), a perfluoroalkylpolymer (“PFA”), a styrene acrylonitrile copolymer (“SAN”), and acombination thereof.

In some exemplary embodiments, in a case where the flexible displaydevice 1 is implemented as a transparent flexible display device, theflexible substrate 110 may include or be formed of a transparent softmaterial.

In an exemplary embodiment of manufacturing a flexible display device,the flexible substrate 110 may be formed by applying a plastic material,to a predetermined thickness, on the top surface of a release layerwhich is disposed on a relatively thick carrier substrate, and curingthe plastic material. Here, the carrier substrate may be separated fromthe flexible substrate 110 by releasing the release layer such asthrough a laser release process.

The pixel array layer 120 may be provided on the flexible substrate 110and may be controlled or driven to display an image. Specifically, thepixel array layer 120 may be disposed on the top surface of the flexiblesubstrate 110. The top surface of the flexible substrate 110 may be asurface of the flexible substrate 110 in an emission direction in whichlight is transmitted in a thickness direction. The definition of the topand bottom surfaces of the flexible substrate 110 may apply throughoutthe description that follows.

The pixel array layer 120 may be disposed on the flexible substrate 110in the main area MA and may include a plurality of pixels which arecontrolled or driven to display an image. Although not specificallyillustrated, the pixel array layer 120 may include thin-film transistors(“TFTs”), anode electrodes, an organic light-emitting layer (“EL”) andcathode electrodes.

The thin-film transistors may be provided in transistor areas of thepixels disposed on the flexible substrate 110 and may include aplurality of conductive layers and a plurality of insulating layers.Here, the thin-film transistors may be a-Si thin-film transistors,poly-Si thin-film transistors, oxide thin-film transistors or organicthin-film transistors.

The anode electrodes may be provided on the thin-film transistors andmay be connected to the thin-film transistors. The anode electrodes mayinclude indium tin oxide (“ITO”), indium zinc oxide (“IZO”), zinc oxide(ZnO) or indium oxide (In₂O₃). In a case where the flexible displaydevice 1 is of a top emission type, the anode electrodes may furtherinclude silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt),palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir),chromium (Cr), lithium (Li), calcium (Ca), or a combination thereof.

The organic light-emitting layer may be disposed or formed on the anodeelectrodes. The display panel DP may include a hole injection layer(“HIL”) and/or a hole transport layer (“HTL”) disposed between theorganic light-emitting layer and the anode electrodes and may furtherinclude an electron transport layer (“ETL”) and/or an electron injectionlayer (“EIL”) disposed between the organic light-emitting layer and thecathode electrodes.

The cathode electrodes may be disposed on the organic light-emittinglayer. In an exemplary embodiment, the cathode electrodes may bedisposed or formed on the entire organic light-emitting layer. Thecathode electrodes may include Li, Ca, LiF/Ca, LiF/Al, Al, Mg, Ag, Pt,Pd, Ni, Au Nd, Ir, Cr, BaF, Ba, or a combination thereof (e.g., thecombination of Ag and Mg). In a case where the flexible display device 1is of a top emission type, a relatively thin conductive material layermay be formed as the cathode electrodes. The cathode electrodes mayfurther include a transparent conductive film disposed on the thinconductive material layer. The transparent conductive film may includeindium tin oxide, indium zinc oxide, zinc oxide, or indium tin zincoxide.

The thin encapsulation layer 130 may be disposed on the pixel arraylayer 120. The thin encapsulation layer 130, which is for reducing oreffectively preventing the infiltration of moisture into the pixels, maybe disposed or formed to cover the pixel array layer 120. Although notspecifically illustrated, the thin encapsulation layer 130 may be alayer in which at least one inorganic film and at least one organic filmare alternately stacked. In an exemplary embodiment, for example, thethin encapsulation layer 130 may include a first inorganic film, anorganic film, and a second inorganic film that are sequentially stacked.

The display panel DP may further include a barrier layer (notillustrated) provided on the thin encapsulation layer 130. The barrierlayer may reduce or effectively prevent the infiltration of moistureinto the pixels. The barrier layer may include a material having arelatively low moisture permeability such as, for example, a polymermaterial.

The display panel DP may further include a polarization film (notillustrated) disposed on the barrier layer. The polarization film mayimprove the optical characteristics of the display panel DP by reducingor effectively preventing the reflection of external light.

As illustrated in FIGS. 2 and 3, the driving member 200 may be a driverintegrated chip. In an exemplary embodiment, for example, the driverintegrated chip may be attached to the display panel DP, which includesa plastic substrate, in a chip-on-plastic (“COP”) manner. The driverintegrated chip may be attached to a flexible film in a chip-on-film(“COF”) manner to be connected to the display area DA. The drivingmember 200 may be attached to the pad area of the display panel DP.Specifically, in the pad area of the display panel DP, a plurality ofpad terminals (not illustrated) may be provided, and bumps (notillustrated) of the driving member 200 may be electrically connected tothe pad terminals of the display panel DP.

The flexible substrate 110 includes the signal wiring 150, whichtransmits external signals to the display area DA, such as to the pixelsof the display panel DP. The signal wiring 150 connected to the pixelsof the display panel DP may extend from one side of the display area DAand may be connected to the driving member 200 corresponding to the padarea. That is, the display area DA and the driving member 200 may beelectrically connected by the signal wiring 150.

The signal wiring 150 may include or be formed of a conductive material,particularly, a conductive material with excellent ductility, tominimize cracks. In an exemplary embodiment, for example, the signalwiring 150 may include or be formed of a conductive material withexcellent ductility such as gold, silver, or aluminum, but the materialof the signal wiring 150 is not particularly limited. The signal wiring150 may include or be formed of various conductive materials that can beused to fabricate components or devices of the display panel DP, likethose within the display area DA of the display panel DP. Specifically,the signal wiring 150 may also include or be formed of molybdenum (Mo),chromium, titanium (Ti), nickel, neodymium, copper (Cu), or an alloy ofsilver and magnesium. The signal wiring 150 may be disposed or formed tohave a multilayer structure including various conductive materials, forexample, a triple-layer structure of titanium/aluminum/titanium, but thepresent disclosure is not limited thereto.

When the flexible substrate 110 is bent, the flexible substrate 110 maybe stressed due to a tensile force. Also, when the flexible substrate110 is bent, the flexible substrate 110 may be stressed by externalshock, for example, by being placed in contact with the corners of theback plate (310 and 320), which will be described later. For thesereasons, cracks may be generated in the flexible substrate 110, and as aresult, the signal wiring 1:50 on the flexible substrate 110 may bedisconnected.

In an asymmetrical bending structure that will be described, the signalwiring 150 is more likely to be disconnected in the main area MA than inthe sub-area. SA. This will be described later in detail.

A center line CL is defined for the flexible display device 1. A centerline of the display panel DP which will be bent to form the bentflexible display device 1 corresponds to the center line CL thereof.Referring to FIG. 3, for example, the display panel DP and the flexibledisplay device 1 may be bent about the center line CL to dispose anupper thickness of the bent flexible display device 1 above the centerline CL, and a lower thickness below the center line CL. The center lineCL extends in a direction perpendicular to the flexible substrate 110 ata center of an open area (OP′ and OP2 together, hereinafter referencedas “OP”). The flexible substrate 110 may include first and secondflexible substrate portions 111 and 112 opposite to each other withrespect to the center line CL, which may hereinafter be referred to asfirst and second flexible substrates 111 and 112. The first flexiblesubstrate 111 may extend from one side of a portion of the flexiblesubstrate 110 in the main area MA and into the bending area. BA to be incontact with the second flexible substrate 112. The second flexiblesubstrate 112 may be in contact with the first flexible substrate 111and may extend from the first flexible substrate 111 in the bending areaBA to be in contact with a portion of the flexible substrate HO in thesub-area SA.

The back plate (310 and 320) may be disposed on the bottom surface ofthe flexible substrate 110 and may support the display panel DPincluding the flexible substrate 110. In an exemplary embodiment ofmanufacturing a flexible display device, the back plate (310 and 320)may include or be formed by a lamination process following a laserrelease process for separating a carrier substrate from the flexiblesubstrate 110. The back plate (310 and 320) may include a thermoplasticmaterial. In an exemplary embodiment, for example, the back plate (310and 320) may include a polyacrylic material such as polyethyleneterephthalate, polycarbonate, polyether sulfone, polyethylenenaphthalate (“PEN”), or polynorbornene (“PNB”). In an exemplaryembodiment, for example, the back plate (310 and 320) may be athermoplastic film.

The back plate (310 and 320) may include first and second back plates310 and 320, respectively. The first and second back plates 310 and 320may be flat plates. The first back plate 310 may be disposed on a partof the bottom surface of the flexible substrate 110 overlapping with themain area MA in the thickness direction. In an exemplary embodiment, forexample, the first back plate 310 may overlap with the main area MA andmay support the pixel array layer 120 in the main area MA, therebymaintaining the pixel array layer 120 to be flat.

The second back plate 320 may be disposed on a part of the bottomsurface of the flexible substrate 110 overlapping with the sub-area SAin the thickness direction. The second back plate 320 may be disposedbelow the first back plate 310 along the thickness direction when theflexible substrate 110 is bent as shown in FIG. 3. In an exemplaryembodiment, for example, the second back plate 320 may overlap with thesub-area SA and may support the signal wiring 150 and the driving member200 in the sub-area SA, thereby maintaining one end of the flexiblesubstrate 110 in the sub area SA to be flat.

The first and second back plates 310 and 320 are illustrated as notoverlapping with the bending area BA, but the present disclosure is notlimited thereto. Alternatively, a part of the first back plate 310 mayoverlap with the bending area BA.

The first back plate 310 may include a first inner side 311 overlappingor aligned with the border between the main area MA and the firstflexible substrate 111 in the thickness direction. The second back plate320 may include a second inner side 321 overlapping or aligned with theborder between the second flexible substrate 112 and the sub-area SA inthe thickness direction.

The first and second inner sides 311 and 321 of the first and secondback plates 310 and 320 are illustrated as being straight, rather thancurved, but the present disclosure is not limited thereto.Alternatively, one or more among the first and second inner sides 311and 321 may be curved with a predetermined curvature.

The back plate (310 and 320) may include or define the open area OP. Theopen area OP may be an area of the flexible substrate 110 where the backplate (310 and 320) is not disposed. The open area OP may overlap withthe bending area BA in the thickness direction. The open area OP mayhave the same size as the bending area BA, such as along the firstand/or second directions. The open area OP may be disposed between thefirst and second back plates 310 and 320. That is, the first and secondback plates 310 and 320 may be spaced apart from each other by the openarea OP.

The open area OP may include first and second open areas OP1 and OP2.The first open area OP1 may be closer to the main area MA than to thesub-area SA, and the second open area OP2 may be closer to the sub-areaSA than to the main area MA. The first open area OP11 may be adjacent tothe first back plate 310. The second open area OP2 may be adjacent tothe second back plate 320. The first and second back plates 310 and 320may be the same distance apart from the center line CL.

At the open area OP, the flexible display device 1 may be bent to have apredetermined curvature. The open area OP of the back plate (310 and320) is illustrated as having the same size as the bending area BA, butthe present disclosure is not limited thereto. Alternatively, the openarea OP may have a larger or smaller size than the bending area BA.

The buffer member (350 and 360) may be disposed to overlap with a partof the bottom surface of the flexible substrate 110 in the bending areaBA. The buffer member (350 and 350) may include first and second buffermembers 350 and 360. The first buffer member 350 may be disposed on thebottom surface of the first flexible substrate 111, such as beingdisposed directly on the bottom surface of the first flexible substrate111, and may be provided in the first open area OP1. The first buffermember 350 may be disposed adjacent to the main area MA.

The second buffer member 360 may be disposed on the bottom surface ofthe second flexible substrate 112, such as being disposed directly onthe bottom surface of the second flexible substrate 112, and may beprovided in the second open area OP2. The second buffer member 360 maybe disposed adjacent to the sub-area SA.

The first buffer member 350 may be in contact with the first back plate310. The second buffer member 360 may be in contact with the second backplate 320. Specifically, the first buffer member 350 may be in contactwith the first inner side 311 of the first back plate 310 and with thefirst flexible substrate 111. The second buffer member 360 may be incontact with the second inner side 321 of the second back plate 320 andwith the second flexible substrate 112. As will be described later, across-sectional thickness of a part of the first buffer member 350 incontact with the first inner side 311 of the first back plate 310 may begreater than a cross-sectional thickness of a part of the second buffermember 360 in contact with the second inner side 321 of the second backplate 320.

The first inner side 311 of the first back plate 310 may be provided atthe open area OP and may overlap with the border between the main areaMA and the bending area BA of the flexible substrate 110, and the secondinner side 321 of the second back plate 320 may be provided in the openarea OP to be spaced apart from the first inner side 311 of the firstback plate 310 in a direction toward the sub-area SA and may overlapwith the border between the sub-area SA and the bending area BA of theflexible substrate 110. However, the present disclosure is not limitedto this. That is, the first inner side 311 of the first back plate 310and the second inner side 321 of the second back plate 320 may bedisposed in the main area MA and the sub-area SA, respectively, or mayboth be disposed in the bending area BA.

The first and second buffer members 350 and 360 may include athermoplastic material. In an exemplary embodiment, for example, thefirst and second buffer members 350 and 360 may include a polyacrylicmaterial such as polyethylene terephthalate, polycarbonate, polyethersulfone, polyethylene naphthalate, or polynorbornene. In an exemplaryembodiment, for example, the first and second buffer members 350 and 360may be thermoplastic films. The material of the first and second buffermembers 350 and 360 may be the same as the material of the first andsecond back plates 310 and 320. That is, the first and second buffermembers 350 and 360 may be formed as one integral body with the firstand second back plates 310 and 320, but the present disclosure is notlimited thereto. As one integral body, one or more among the first andsecond buffer members 350 and 360 and the first and second back plates310 and 320 may extend or protrude to define one or more of the othersamong the first and second buffer members 350 and 360 and the first andsecond back plates 310 and 320. Alternatively, the material of the firstand second buffer members 350 and 360 may be different from the materialof the first and second back plates 310 and 320. Also, the first andsecond buffer members 350 and 360 may include different materials or thesame material.

The cross-sectional thickness of the first and second buffer members 350and 360 may be smaller than those of the first and second back plates310 and 320 so as not to increase the total thickness of the flexibledisplay device 1, but the present disclosure is not limited thereto.That is, the maximum cross-sectional thickness of the first and secondbuffer members 350 and 360 may be smaller than the minimumcross-sectional thickness of the first and second back plates 310 and320. Alternatively, the cross-sectional thickness of the first and/orsecond buffer members 350 and 360 may be greater than the thickness ofthe first and second back plates 310 and 320. In an exemplaryembodiment, for example, the thickness of the first buffer member 350may be greater than the thickness of the back plate (310 and 320), andthe thickness of the second buffer member 360 may be smaller than thethickness of the back plate (310 and 320). Such thicknesses may beconsidered across an entirety of the buffer members 350 and 360, or atportions thereof closest to and directly adjacent to the back plate (310and 320).

The first and second buffer members 350 and 360 may have the same widthtaken along the first and/or second directions. The width of the firstand second buffer members 350 and 360 may be taken between the centerline CL and a respective back plate (310 or 320). At a portion incontact with the first back plate 310, the first buffer member 350 mayhave a first thickness T₁ defined by a surface furthest from the firstflexible substrate 111. At a portion in contact with the second backplate 320, the second buffer member 360 may have a second thickness T₂defined by a surface furthest from the second flexible substrate 112.The first thickness T₁ may be the maximum thickness of the overall firstbuffer member 350. The second thickness T₂ may be the maximum thicknessof the overall second buffer member 360. The first thickness T₁ may begreater than the second thickness T₂.

Along the first and/or second directions, the average thickness of thefirst buffer member 350 may be greater than the average thickness of thesecond buffer member 360. Also, the volume of the first buffer member350 may be greater than the volume of the second buffer member 360,where volumes are defined by a product of a thickness dimension, a firstdirection dimension and a second direction dimension. The contact areabetween the first buffer member 350 and the bottom surface of theflexible substrate 110 is the same as the contact area between thesecond buffer member 360 and the bottom surface of the flexiblesubstrate 110, such as considering the buffer members 350 and 360symmetrically disposed about the center line. Since the contact areabetween the first buffer member 350 and the bottom surface of theflexible substrate 110 is the same as the contact area between thesecond buffer member 360 and the bottom surface of the flexiblesubstrate 110, the volume of the first and second buffer members 350 and360 may be defined by or comparable with the average thickness of thefirst and second buffer members 350 and 360. The volume (or averagethickness) of the first buffer member 350 in the first open area OP1 maybe asymmetrical with those of the second buffer member 360 in the secondopen area OP2, with respect to the center line CL.

The first thickness T₁ may be smaller than the thickness of the firstback plate 310. The second thickness T₂ may be smaller than thethickness of the second back plate 320. In a case where the secondbuffer member 360 is not disposed in the second open area OP2, thesecond thickness T₂ may be zero, but the present disclosure is notlimited thereto. Alternatively, the first thickness T₁ may be greaterthan the thickness of the first back plate 310, in which case, the firstbuffer member 350 may be disposed on the top surface of the first backplate 310 to be in contact with, and cover, the top surface of the firstback plate 310 at the first inner side 211.

The first and second buffer members 350 and 360 may further include amoisture permeation preventing material. The moisture permeationpreventing material may be disposed or formed as an inorganic film or anorganic film, but the invention is not limited to thereto.Alternatively, the moisture permeation preventing material may be formedas a stack of an inorganic film and an organic film. The first buffermember 350 may cover an area in which the first inner side 311 and thefirst flexible substrate 111 are in contact with each other, and thesecond buffer member 360 may cover an area in which the second innerside 321 and the second flexible substrate 112 are in contact with eachother. That is, the penetration of moisture into the flexible substrate110 can be effectively prevented by the first and second buffer members350 and 360, and peeling of the back plate (310 and 320) from theflexible substrate 110 can be reduced or effectively prevented. In anexemplary embodiment, for example, the moisture permeation preventingmaterial may include a silicone material with excellent thermalstability, excellent adhesiveness, and an excellent moisture permeationprevention function.

The arrangement of the first and second back plates 310 and 320 and thechange of the curvature of the flexible substrate 110 when the flexibledisplay device 1 is bent will hereinafter be described with reference toFIGS. 3 and 4.

FIG. 3 is a cross-sectional view of an exemplary embodiment of theflexible display device of FIG. 1 in a bent state, and FIG. 4 is adetailed cross-sectional view of the bent flexible display device ofFIG. 3. The bent flexible display device of FIGS. 3 and 4 are eachformed by the flexible display device of FIG. 2 which is bent. Forconvenience of illustration, the signal wiring 150 shown in FIG. 2 isomitted from FIGS. 3 and 4.

Referring to FIG. 3, when the flexible display device 1 is bent, a partof the bending area BA may overlap with the main area MA in thethickness direction. That is, dead space in the bent flexible displaydevice 1 can be reduced by reducing the size of the bending area BAdisposed outside of the main area MA of the flexible display device 1along the direction in which the bending area BA and the main area MAare arranged, and making the bending area BA overlap with the main areaMA along the thickness direction.

In the bent flexible display device 1, the second back plate 320 may bedisposed below the first back plate 310 in the thickness direction.

Although not specifically illustrated, the bent flexible display device1 may further include heat dissipation sheets, cushion sheets, agraphite layer, and a plurality of adhesive layers between the first andsecond back plates 310 and 320 which are disposed facing each other asillustrated in FIG. 3.

The heat dissipation sheets may be disposed on the back plate (310 and320). Each of the heat dissipation sheets may have a stack of multiplelayers. Each of the heat dissipation sheets may include two layers, andthe two layers may be disposed on the first and second back plates 310and 320. The heat dissipation sheets may include a metal material. In anexemplary embodiment, for example, the heat dissipation sheets may beformed as relatively thin copper sheets, but the present disclosure isnot limited thereto. The material of the heat dissipation sheets may beappropriately chosen. Since a metal material has excellent thermalconductivity, the heat dissipation sheets, which include or are formedof a metal material, can improve the thermal conductivity of theflexible display device 1. Accordingly, heat generated in the flexibledisplay device 1 can be efficiently released, and as a result, the heatdissipation efficiency of the flexible display device 1 can be improved.

The cushion sheets may be disposed on the heat dissipation sheets. Thecushion sheets may be disposed between the heat dissipation sheets. Twocushion sheets may be provided and may be disposed to be spaced apartfrom each other in a direction in which the flexible substrate 110extends. The cushion sheets may include or be formed as elastic members.In an exemplary embodiment, for example, the cushion sheets may includeor be formed of a material such as polyurethane and may thus be able toabsorb shock from the outside or the inside thereof. In an exemplaryembodiments, the cushion sheets may be shock mitigation layers.Accordingly, the durability of the flexible display device 1 can befurther improved. However, the material of the cushion sheets is notparticularly limited. That is, the material of the cushion sheets may beappropriately chosen from among a variety of elastic materials.

The graphite layer may be disposed between the two cushion sheets, butthe present disclosure is not limited thereto. The graphite layer may bedisposed on the cushion sheets. The graphite layer may include carbonpowder and may thus improve thermal conductivity. Accordingly, thethermal conductivity of the flexible display device 1 can be improved,and heat generated in the flexible display device 1 can be efficientlyreleased.

The heat dissipation sheets, the cushion sheets, and the graphite layermay be bonded to one another via adhesive layers, but the presentdisclosure is not limited thereto. The heat dissipation sheets, thecushion sheets, and the graphite layer may be placed in contact with oneanother without any layers disposed therebetween. The heat dissipationsheets may be attached to the first and second back plates 310 and 320via adhesive layers.

As illustrated in FIG. 3, an end of the bent flexible display device 1is disposed at the left of the view. With reference to the end of thebent flexible display device 1, the second inner side 321 of the secondback plate 320 may be disposed further inside than the first inner side311 of the first back plate 310. That is, a portion the flexible displaydevice 1 at the first inner side 311 of the first back plate 310 maydefine a maximum dimension of the bending area BA which is visible at anemission side of the flexible display device 1, since remaining portionsof the flexible display device 1 are disposed further inside thisportion of the flexible display device 1. This maximum dimension of thebending area BA which is visible at an emission side of the flexibledisplay device 1 may define a bezel width of the flexible display device1.

Specifically, as illustrated in FIG. 4, the first inner side 311 of thefirst back plate 310 may include a first contact point 111P where thefirst inner side 311 of the first back plate 310 is in contact with thefirst flexible substrate 111, and the second inner side 321 of thesecond back plate 320 may include a second contact point 112P where thesecond inner side 321 of the second back plate 320 is in contact withthe second flexible substrate 112. The flexible substrate 110 mayinclude a first intersection point CP₁ where the flexible substrate 110intersects the center line CL.

As a dotted line feature in FIGS. 3 and 4, the flexible substrate 110may be bent symmetrically when the inner side 311 of the first backplate 310 and the second inner side 321 of the second back plate 320overlap or align with each other in the thickness direction. When theflexible substrate 110 is bent symmetrically, as illustrated by thedotted line feature in FIGS. 3 and 4, the flexible substrate 110 mayinclude a second intersection point CP₂ where the flexible substrate 110intersects the center line CL.

An extension line connecting the first contact point 111P and the firstintersection point CP₁ may form a first line Line1. An extension lineconnecting the second contact point 112P and the first intersectionpoint CP₁ may form a second line Line2. An extension line connecting thefirst contact point 111P and the second intersection point CP₂ may forma third line Line3.

The first line Line1 may form a first average bending angle θ1 with thecenter line CL. The second line Line2 may form a second average bendingangle θ2 with the center line CL. The third line Line3 may form a thirdaverage bending angle θ3 with the center line CL. The first, second, andthird average bending angles θ1, θ2, and θ3 may all be acute angles. Thetangent values of the first, second, and third average bending anglesθ1, θ2, and θ3 may form an average bending slope. Accordingly, the firstflexible substrate 111 may have the first average bending angle θ1 and afirst average bending slope (SLOPE 1), and the second flexible substrate112 may have the second average bending angle θ2 and a second averagebending slope (SLOPE 2).

In an exemplary embodiment, the first average bending angle θ1 may begreater than the second and third average bending angles θ2 and θ3, thesecond average bending angle θ2 may be smaller than the first and thirdaverage bending angles θ1 and θ3, and the third average bending angle θ3may be smaller than the first average bending angle θ1 and may begreater than the second average bending angle θ2. Similarly, the firstaverage bending slope (SLOPE 1) may be greater than the second and thirdaverage bending slopes (SLOPE 2 and SLOPE 3), the second average bendingslope (SLOPE 2) may be smaller than the first and third average bendingslopes (SLOPE 1 and SLOPE 3), and the third average bending slope (SLOPE3) may be smaller than the first average bending slope (SLOPE 1) and maybe greater than the second average bending slope (SLOPE 2). However, thepresent disclosure is not limited to this. Alternatively, the secondaverage bending slope (SLOPE 2) may become greater than the thirdaverage bending slope (SLOPE 3) depending on the degree to which thesecond back plate 320 is recessed in a direction away from the end ofthe bent flexible display device 1.

The first flexible substrate 111 may have a first average curvature(CV1). The second flexible substrate 112 may have a second averagecurvature (CV2). Since the first average bending slope (SLOPE 1) isgreater than the second and third average bending slopes (SLOPE 2 andSLOPE 3), the first average curvature (CV1) may be greater than thesecond and third average curvatures (CV2 and CV3). The second averagecurvature (CV2) may be smaller than the first and third averagecurvatures (CV1 and CV3). The third average curvature (CV3) may besmaller than the first average curvature (CV1) and may be greater thanthe second average curvature (CV2).

Since the first and second flexible substrates 111 and 112 haveasymmetrical average bending angles, asymmetrical average bendingslopes, and asymmetrical average curvatures, the flexible substrate 110may be bent asymmetrically. When the flexible substrate 110 is bentasymmetrically, a part of the bending area BA which is outside of themain area MA in a flat state of the flexible display device 1, may bedisposed to overlap the main area MA in a bent state of the flexibledisplay device. As a result, the bezel width of the flexible displaydevice 1 can be reduced. Accordingly, an essentially bezel-less flexibledisplay device can be provided.

However, the stress applied to the first flexible substrate 111 may begreater when the flexible substrate 110 is bent asymmetrically than whenthe flexible substrate 110 is bent symmetrically. Also, the stressapplied to the first flexible substrate 111 may be greater than thestress applied to the second flexible substrate 112.

Since the average bending angle, the average bending slope, and theaverage curvature of the first flexible substrate 111 are greater thanthe average bending angle, the average bending slope, and the averagecurvature of the second flexible substrate 112, the first flexiblesubstrate 111 may be bent to a greater extent than the second flexiblesubstrate 112. Accordingly, when the flexible substrate 110 is bent, thefirst flexible substrate 111 may receive more stress than the secondflexible substrate 112. Also, since the contact force between the firstflexible substrate 111 and the first contact 111P of the first innersurface 311 of the first back plate 310 is greater than the contactforce between the second flexible substrate 112 and the second contactpoint 112P of the second inner surface 321 of the second back plate 320,the first flexible substrate 111 may receive more stress than the secondflexible substrate 112. That is, the stress applied to the flexiblesubstrate 110 may be greater in the first flexible substrate 111 than inthe second flexible substrate 112. As a result, cracks may be generatedin the signal wiring 150 on the first flexible substrate 111, andeventually, the signal wiring 150 may be disconnected.

However, since the buffer member (350 and 360) is applied asymmetricallyto the flexible substrate 110, the stress caused by the asymmetricbending of the flexible substrate 110 can be alleviated. In addition,the buffer member (350 and 360) can reduce or effectively preventpeeling of the flexible substrate 110 and the back plate (310 and 320)from each other, and can also reduce or effectively prevent thepenetration of moisture between the flexible substrate 110 and the backplate (310 and 320). Specifically, since the average thickness of thefirst buffer member 350 and the volume of the first buffer member 350which is in contact with the flexible substrate 110 are greater than theaverage thickness of the second buffer member 360 and the volume of thesecond buffer member 360 which is in contact with the flexible substrate110, the first buffer member 350 can properly perform a buffer functionwhile guiding the bending of the first flexible substrate 111, whichreceives more stress than the second flexible substrate 112.Accordingly, a reliable flexible display device can be provided byreducing or effectively preventing the disconnection of the signalwiring 150.

FIGS. 5A and 5B are cross-sectional views illustrating the formation ofthe buffer member (350 and 360) in the bending area BA. The step offorming the buffer member (350 and 360) in the bending area BA willhereinafter be described with reference to FIGS. 5A and 5B.

Referring to FIG. 5A, a heating block 400 may be disposed on apreliminary buffer member in the bending area BA. The heating block 400may include first, second, and third heating areas 410, 420, and 430.The first heating area 410 may be an area on the left side of theheating block 400. The second heating area 420 may be an area on theright side of the heating block 400. The third heating area 430 may bean area between the first and second heating areas 410 and 420. Thepreliminary buffer member may include first, second, and third bufferareas 341, 342 and 343. The first buffer area 341 may be an area on theleft side of the preliminary buffer member. The second buffer area 342may be an area on the right side of the preliminary buffer member (341,342 and 343). The third buffer area 343 may be an area between the firstand second buffer areas 341 and 342. The first, second, and third bufferareas 341, 342, and 343 of the preliminary buffer member (341, 342 and343) may have substantially the same thickness taken from the flexiblesubstrate 110, before being in contact with the heating block 400. Aftercontacting by the heating block 400, the first, second, and third bufferareas 341, 342, and 343 of the preliminary buffer member may havedifferent thicknesses.

The first and second heating areas 410 and 420 may have a smallerthickness than the third heating area 430. That is, the third heatingarea 430 may protrude toward the flexible display device 1 further thanthe first and second heating areas 410 and 420. The third heating area430 may have a flat surface area having a predetermined width. Theaverage thickness of the first heating area 410 may be smaller than theaverage thickness of the second heating area 420. The average thicknessof the second heating area 420 may be greater than the average thicknessof the first heating area 410.

The first heating area 410 may contact with the first buffer area 341.The second heating area 420 may contact with the second buffer area 342.The third heating area 430 may contact with the third buffer area 343.Specifically, after contacting the heating block 400, the first bufferarea 341 may become thicker than the second buffer area 342. Also, thefirst buffer area 341 may have a greater width along the horizontaldirection in FIG. 5A than the second buffer area 342.

When placed in contact with the heating block 400, which has apredetermined shape, the preliminary buffer member (341, 342 and 343)may be melted by the thermal energy of the heating block 400 and may bemolded into a shape corresponding to the shape of the heating block 400.

Referring to FIG. 5B, which shows a process of placing the heating block400 and the preliminary buffer member (341, 342 and 343) in contact witheach other, parts the preliminary buffer member (341, 342 and 343) maybe melted in the order they are placed in contact with the heating block400. The melted preliminary buffer member (341, 342 and 343) may havefluid mobility, and as a result, a fine flow may be generated in thepreliminary buffer member (341, 342 and 343). The fluid mobility of themelted preliminary buffer member (341, 342 and 343) may vary dependingon the pressing force of the heating block 400 against the preliminarybuffer member (341, 342 and 343) and/or the temperature of the heatingblock 400. Specifically, the greater the pressing force of the heatingblock 400, the greater the fluid mobility of the melted preliminarybuffer member (341, 342 and 343). On the contrary, the smaller thepressing force of the heating block 400, the smaller the fluid mobilityof the melted preliminary buffer member (341, 342 and 343). Also, thehigher the temperature of the heating block 400, the greater the fluidmobility of the melted preliminary buffer member (341, 342 and 343). Onthe contrary, the lower the temperature of the heating block 400, thesmaller the fluid mobility of the melted preliminary buffer member (341,342 and 343).

In this manner, the melted preliminary buffer member (341, 342 and 343)may be formed into the shape of the buffer member (350 and 360) of FIG.2.

FIG. 6 is a cross-sectional view of another exemplary embodiment of aflexible display device in a bent state according to the presentdisclosure.

Referring to FIG. 6, a flexible display device 2 differs from theflexible display device 1 of FIGS. 2 through 5 in that a first buffermember 350 a is disposed to extend over to a first back plate 310 a whena flexible substrate 110 a is bent.

Specifically, the first buffer member 350 a may include or define afirst extension member 351 a extending over to the bottom of the firstback plate 310 a from an end of the bent flexible display device 2. Thatis, the first extension member 351 a may extend from the first buffermember 350 a and may be disposed on the bottom surface of the first backplate 310 a, such as being disposed directly on the bottom surface ofthe first back plate 310 a. The first extension member 351 a may have athickness T₃ in a thickness direction of the flexible display device 2.A maximum thickness T₁ of the first buffer member 350 a, which includesor extends to define the first extension member 351 a, may be greaterthan a maximum thickness T₂ of a second buffer member 360 a and may alsobe greater than the thickness of the first back plate 310 a. In thiscase, the first extension member 351 a may overlap with a part of asecond back plate 320 a in the thickness direction. When the flexiblesubstrate 110 a is bent, the first extension member 351 a can minimizeinterference between the bottom surface of the first back plate 310 aand the bottom surface of the second back plate 320 a, which is disposedat the bottom of the first back plate 310 a, and can mitigate shocktransmitted between the first and second back plates 310 a and 320 a.

In the exemplary embodiment of FIG. 6, like in the exemplary embodimentof FIGS. 2 through 5, an asymmetric buffer member (350 a and 351 a) maybe used. That is, the stress applied to the first flexible substrate 111a may be greater when the flexible substrate 110 a is bentasymmetrically than when the flexible substrate 110 a is bentsymmetrically. Also, the stress applied to the first flexible substrate111 a may be greater than the stress applied to the second flexiblesubstrate 112 a.

Since the average bending angle, the average bending slope, and theaverage curvature of the first flexible substrate 111 a are greater thanthe average bending angle, the average bending slope, and the averagecurvature of the second flexible substrate 112 a, the first flexiblesubstrate 111 a may be bent to a greater extent than the second flexiblesubstrate 112 a. Accordingly, when the flexible substrate 110 a is bent,the first flexible substrate 111 a may receive more stress than thesecond flexible substrate 112 a. Also, since the first flexiblesubstrate 111 a has a relatively strong contact force with a firstcontact 111P of a first inner surface 311 a of the first back plate 310a, the first flexible substrate 111 a may receive more stress than thesecond flexible substrate 112 a. That is, the stress applied to theflexible substrate 110 a may be greater in the first flexible substrate111 a than in the second flexible substrate 112 a. As a result, cracksmay be generated in signal wiring on the first flexible substrate 111 a,and eventually, the signal wiring may be disconnected.

However, since the buffer member (350 a and 360 a) is appliedasymmetrically to the flexible substrate 110 a, the stress caused by theasymmetric bending of the flexible substrate 110 a can be alleviated. Inaddition, the buffer member (350 a and 360 a) can reduce or effectivelyprevent peeling of the flexible substrate 110 a and a back plate (310 aand 320 a) from each other, and can also reduce or effectively preventthe penetration of moisture between the flexible substrate 110 a and theback plate (310 a and 320 a). Specifically, since the average thicknessand the volume of the first buffer member 350 a are greater than theaverage thickness and the volume of the second buffer member 360 a, thefirst buffer member 350 a can properly perform a buffer function whileguiding the bending of the first flexible substrate 111 a, whichreceives more stress than the second flexible substrate 112 a.Accordingly, a reliable flexible display device can be provided byreducing or effectively preventing the disconnection of the signalwiring.

FIG. 7 is a cross-sectional view of still another exemplary embodimentof a flexible display device in a bent state according to the presentdisclosure, and FIG. 8 is an enlarged cross-sectional view of theflexible display device of FIG. 7.

Referring to FIGS. 7 and 8, a flexible display device 3 differs from theflexible display device 1 of FIGS. 2 through 5 in that it furtherincludes a third buffer member 370 b disposed on the top surface of aflexible substrate 110 b in a bending area BA.

Specifically, the flexible display device 3 may include first and secondbuffer members 350 b and 360 b and may further include the third buffermember 370 b. The third buffer member 370 b may be disposed on theflexible substrate 110 b to face the first and second buffer members 350b and 360 b. The third buffer member 370 b may be disposed on the topsurface of the flexible substrate 110 b. Specifically, the third buffermember 370 b may cover the top surfaces of first and second flexiblesubstrates 111 b and 112 b, but the present disclosure is not limitedthereto. Alternatively, the third buffer member 370 b may further extendto the outside of the first and second flexible substrates 111 b and 112b.

When the flexible substrate 110 b is bent, a plane where strain causedby the bending of the flexible substrate 110 b substantially becomeszero may be defined as a neutral plane CS. The neutral plane CS may beformed by the third buffer member 370 b, which faces the first andsecond buffer members 350 b and 360 b disposed on the top surface andthe bottom surface, respectively, with respect to the flexible substrate110 b.

When the third buffer member 370 b is used, signal wiring disposed in adisplay area DA and a part of a non-display area NDA of the flexiblesubstrate 110 b can be essentially placed on the neutral plane CS by thefirst, second, and third buffer members 350 b, 360 b, and 370 b.

The first, second, and third buffer members 350 b, 360 b, and 370 b mayinclude or be formed of the same material, but the present disclosure isnot limited thereto.

Alternatively, the first, second, and third buffer members 350 b, 360 b,and 370 b may include or be formed of different materials. In this case,the lengths, thicknesses, and elasticity moduli of the first, second,and third buffer members 350 b, 360 b, and 370 b may be adjusted so asto place the signal wiring on the neutral plane CS. In an exemplaryembodiment, for example, the first and second buffer members 350 b and360 b may be thicker than the third buffer member 370 b, but may have alower elasticity modulus than the third buffer member 370 b so that thesignal wiring in the non-display area NDA of the flexible substrate 110b can be placed on the neutral plane CS by the first, second, and thirdbuffer members 350 b, 360 b, and 370 b. Thicknesses of the first,second, and third buffer members 350 b, 360 b, and 370 b may be taken ina substantially normal direction to the flexible substrate 110 b atrespective positions along the flexible substrate 110 b.

The length and the thickness of the third buffer member 370 b may bedesigned in various manners in comparison to the lengths and thethicknesses of the first and second buffer members 350 b and 360 b. Inan exemplary embodiment, for example, the third buffer member 370 b maybe thinner than the first and second buffer members 350 b and 360 b, andthe maximum thickness of the third buffer member 370 b may be smallerthan the maximum thicknesses of the first and second buffer members 350b and 360 b. In this example, the third buffer member 370 b may have ahigher elasticity modulus than the first and second buffer members 350 band 360 b, but the present disclosure is not limited thereto.

In the exemplary embodiment of FIGS. 7 and 8, like in the exemplaryembodiments of FIGS. 2 through 5 and FIG. 6, an asymmetric buffer member(350 b and 360 b) may be used. That is, the stress applied to the firstflexible substrate 111 b may be greater when the flexible substrate 110b is bent asymmetrically than when the flexible substrate 110 b is bentsymmetrically. Also, the stress applied to the first flexible substrate111 b may be greater than the stress applied to the second flexiblesubstrate 112 b.

Since the average bending angle, the average bending slope, and theaverage curvature of the first flexible substrate 111 b are greater thanthe average bending angle, the average bending slope, and the averagecurvature of the second flexible substrate 112 b, the first flexiblesubstrate 111 b may be bent to a greater extent than the second flexiblesubstrate 112 b. Accordingly, when the flexible substrate 110 b is bent,the first flexible substrate 111 b may receive more stress than thesecond flexible substrate 112 b. Also, since the first flexiblesubstrate 111 b has a relatively strong contact force with a firstcontact 111P of a first inner surface 311 b of the first back plate 310b, the first flexible substrate 111 b may receive more stress than thesecond flexible substrate 112 b. That is, the stress applied to theflexible substrate 110 b may be greater in the first flexible substrate111 b than in the second flexible substrate 112 b. As a result, cracksmay be generated in signal wiring on the first flexible substrate 111 b,and eventually, the signal wiring may be disconnected.

However, since the buffer member (350 b and 360 b) is appliedasymmetrically to the flexible substrate 110 b, the stress caused by theasymmetric bending of the flexible substrate 110 b can be alleviated. Inaddition, the buffer member (350 b and 360 b) can reduce or effectivelyprevent peeling of the flexible substrate 110 b and a back plate (310 band 320 b) from each other, and can also reduce or effectively preventthe penetration of moisture between the flexible substrate 110 b and theback plate (310 b and 320 b). Specifically, since the average thicknessand the volume of the first buffer member 350 b are greater than theaverage thickness and the volume of the second buffer member 360 b, thefirst buffer member 350 b can properly perform a buffer function whileguiding the bending of the first flexible substrate 111 b, whichreceives more stress than the second flexible substrate 112 b.Accordingly, a reliable flexible display device can be provided byreducing or effectively preventing the disconnection of the signalwiring.

FIG. 9 is a cross-sectional view of yet another exemplary embodiment ofa flexible display device in a bent state according to the presentdisclosure.

Referring to FIG. 9, a flexible display device 4 differs from theflexible display device 1 of FIGS. 2 through 5 in that it includes afirst back plate 310 c including a first curved surface S1 on a firstinner side 311 c thereof, but does not include a buffer member.

Specifically, the first back plate 310 c may include the first curvedsurface S1, to which a first curvature (CV1) is applied, on the firstinner side 311 c, which protrudes toward a first flexible substrate 111c. FIG. 9 illustrates that the first inner side 311 c of the first backplate 310 c includes the first curved surface S1, to which the firstcurvature (CV1) is applied, and no curvature is applied to the secondinner side 321 c of the second back plate 320 c, but the presentdisclosure is not limited thereto. Alternatively, the second back plate320 c may include a second curved surface, to which the second curvature(CV2) is applied, on the second inner side 321 c, which protrudes towarda second flexible substrate 112 c.

The first curved surface S1 of the first inner side 311 c is illustratedas having a semicircular shape, but the present disclosure is notlimited thereto. Alternatively, the first curved surface S1 of the firstinner side 311 c may have a quadrant shape to which the first curvature(CV1) is applied, and the second curved surface of the second inner side321 c may have a quadrant shape to which the second curvature (CV2) isapplied.

The first and second curvatures (CV1 and CV2) may be designed inconsideration of various factors such as the type of the flexiblesubstrate 110 c, the degree to which the flexible substrate 110 c isbent, and the material, the thickness, and the elasticity modulus of abuffer member. Thus, the first and second curvatures (CV1 and CV2) maybe the same or may be different. In the exemplary embodiment of FIG. 9,the first curvature (CV1) may be greater than the second curvature(CV2).

When the first and second back plates 310 c and 320 c having the firstand second curvatures (CV1 and CV2), respectively, are used, stress canbe considerably reduced when the flexible substrate 110 c is placed incontact with the first and second back plates 310 c and 320 c.Particularly, in an asymmetric bending structure, the stress of thefirst flexible substrate 111 c can be reduced by making the firstcurvature (CV1) greater than the second curvature (CV2).

Specifically, by making the first curvature (CV1) of the first backplate 310 c greater than the second curvature (CV2) of the second backplate 320 c, the stress of the first flexible substrate 111 c, which ismore stressed than the second flexible substrate 112 c, can be reduced,and the disconnection of signal wiring can be reduced or effectivelyprevented. Accordingly, a reliable flexible display device can beprovided.

FIG. 10 is a cross-sectional view of yet another exemplary embodiment ofa flexible display device in a bent state according to the presentdisclosure.

Referring to FIG. 10, a flexible display device 5 differs from theflexible display device 1 of FIGS. 2 through 5 in that it includes afirst back plate 310 d including a first curved surface S1 on a firstinner side 311 d thereof.

FIG. 10 illustrates that the first inner side 311 d of the first backplate 310 d includes the first curved surface S1, to which the firstcurvature (CV1) is applied, and no curvature is applied to the secondinner side 321 d of the second back plate 320 d, but the presentdisclosure is not limited thereto. Alternatively, the second back plate320 d may include a second curved surface, to which the second curvature(CV2) is applied, on the second inner side 321 d, which protrudes towarda second flexible substrate 112 d. The first curved surface S1 of thefirst back plate 310 d and the second curved surface of the second backplate 320 d are as described above with reference to FIG. 9, and thus,detailed descriptions thereof will be omitted.

The flexible display device 5 may further include a buffer member (350 dand 360 d) in contact with the first and second back plates 310 d and320 d, to which first and second curvatures (CV1 and CV2), respectively,are applied.

The thickness of a part of a first buffer member 350 d that is incontact with the first curved surface S1 of the first inner side 311 dof the first back plate 310 d may be greater than the thickness of apart of a second buffer member 360 d that is in contact with the secondinner side 321 d of the second back plate 320 d.

FIG. 10 illustrates that the first inner side 311 d of the first backplate 310 d includes the first curved surface S1, to which the firstcurvature (CV1) is applied, and no curvature is applied to the secondinner side 321 d of the second back plate 320 d, but the presentdisclosure is not limited thereto. Alternatively, the second back plate320 d may include a second curved surface, to which the second curvature(CV2) is applied, on the second inner side 321 d, which protrudes towarda second flexible substrate 112 d.

The first and second buffer members 350 d and 360 d and the first andsecond back plates 310 d and 320 d may include the same material and maybe formed in one integral body with one another.

As described above with reference to FIG. 6, the first buffer member 350d may include or define a first extension member (351 a in FIG. 6)extending over to the bottom of the first back plate 310 d. That is, thefirst extension member may extend from the first buffer member 350 d andmay be disposed on the bottom surface of the first back plate 310 d,such as being disposed directly on the bottom surface of the first backplate 310 d. The first extension member may have a thickness (T₃ in FIG.6) in a thickness direction of the flexible display device 5. A maximumthickness (T₁ in FIG. 6) of the first buffer member 350 d, whichincludes or defines the first extension member, may be greater than amaximum thickness (T₂ in FIG. 6) of the second buffer member 360 d andmay also be greater than the thickness of the first back plate 310 d.

As described above with reference to FIGS. 2 through 5, the buffermember (350 d and 360 d) may be applied asymmetrically.

Due to the asymmetric bending of a flexible substrate 110 d, the stressapplied to the first flexible substrate 111 d may be greater when theflexible substrate 110 d is bent asymmetrically than when the flexiblesubstrate 110 d is bent symmetrically. Also, the stress applied to thefirst flexible substrate 111 d may be greater than the stress applied tothe second flexible substrate 112 d.

Since the average bending angle, the average bending slope, and theaverage curvature of the first flexible substrate 111 d are greater thanthe average bending angle, the average bending slope, and the averagecurvature of the second flexible substrate 112 d, the first flexiblesubstrate 111 d may be bent to a greater extent than the second flexiblesubstrate 112 d. Accordingly, when the flexible substrate 110 d is bent,the first flexible substrate 111 d may receive more stress than thesecond flexible substrate 112 b. Also, since the first flexiblesubstrate 111 d has a relatively strong contact force with a firstcontact 111P of the first inner surface 311 d of the first back plate310 d, the first flexible substrate 111 d may receive more stress thanthe second flexible substrate 112 d. That is, the stress applied to theflexible substrate 110 d may be greater in the first flexible substrate111 d than in the second flexible substrate 112 d. As a result, cracksmay be generated in signal wiring on the first flexible substrate 111 d,and eventually, the signal wiring may be disconnected.

When the first and second back plates 310 d and 320 d having the firstand second curvatures (CV1 and CV2), respectively, are used, stress canbe considerably reduced when the flexible substrate 110 d is placed incontact with the first and second back plates 310 d and 320 d.Particularly, in an asymmetric bending structure, the stress of thefirst flexible substrate 111 d can be reduced by making the firstcurvature (CV1) greater than the second curvature (CV2).

FIG. 11 is a cross-sectional view of yet another exemplary embodiment ofa flexible display device in a bent state according to the presentdisclosure.

Referring to FIG. 11, a flexible display device 6 differs from theflexible display device 1 of FIGS. 2 through 5 in that it includes afirst back plate 310 e including a first curved surface S1 on a firstinner side 311 e thereof where a second back plate 320 e includes asecond inner side 321 e thereof, and further includes a third buffermember 370 e on the top surface of a flexible substrate 110 e. The thirdbuffer member 370 e, which is disposed on the top surface of theflexible substrate 110 e to face first and second buffer members 350 eand 360 e, is as described above with reference to FIGS. 7 and 9, andthus, a detailed description thereof will be omitted.

As described above with reference to FIGS. 7 and 8, when the thirdbuffer member 370 e is used, signal wiring disposed in a display area DAand a part of a non-display area NDA of the flexible substrate 110 e canbe placed on a neutral plane CS by the first, second, and third buffermembers 350 e, 360 e, and 370 e.

In the exemplary embodiment of FIG. 11, like in the exemplaryembodiments of FIGS. 2 through 5, FIG. 6, and FIGS. 7 and 8, anasymmetric buffer member (350 e and 360 e) may be used. That is, thestress applied to a first flexible substrate 111 e may be greater whenthe flexible substrate 110 e is bent asymmetrically than when theflexible substrate 110 e is bent symmetrically. Also, the stress appliedto the first flexible substrate 111 e may be greater than the stressapplied to a second flexible substrate 112 e.

Since the average bending angle, the average bending slope, and theaverage curvature of the first flexible substrate 111 e are greater thanthe average bending angle, the average bending slope, and the averagecurvature of the second flexible substrate 112 e, the first flexiblesubstrate 111 e may be bent to a greater extent than the second flexiblesubstrate 112 e. Accordingly, when the flexible substrate 110 e is bent,the first flexible substrate 111 e may receive more stress than thesecond flexible substrate 112 e. Also, since the first flexiblesubstrate 111 e has a relatively strong contact force with a firstcontact 111P of a first inner surface 311 e of the first back plate 310e, the first flexible substrate 111 e may receive more stress than thesecond flexible substrate 112 e. That is, the stress applied to theflexible substrate 110 e may be greater in the first flexible substrate111 e than in the second flexible substrate 112 e. As a result, cracksmay be generated in signal wiring on the first flexible substrate 111 e,and eventually, the signal wiring may be disconnected.

However, since the buffer member (350 e and 360 e) is appliedasymmetrically to the flexible substrate 110 e, the stress caused by theasymmetric bending of the flexible substrate 110 e can be alleviated. Inaddition, the buffer member (350 e and 360 e) can reduce or effectivelyprevent peeling of the flexible substrate 110 e and a back plate (310 eand 320 e) from each other, and can also reduce or effectively preventthe penetration of moisture between the flexible substrate 110 e and theback plate (310 e and 320 e). Specifically, since the average thicknessand the volume of the first buffer member 350 e are greater than theaverage thickness and the volume of the second buffer member 360 e, thefirst buffer member 350 e can properly perform a buffer function whileguiding the bending of the first flexible substrate 111 e, whichreceives more stress than the second flexible substrate 112 e.Accordingly, a reliable flexible display device can be provided byreducing or effectively preventing the disconnection of the signalwiring 150 e.

Although the exemplary embodiments of the invention have been disclosedfor illustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

What is claimed is:
 1. A display device comprising: a flexible substrateincluding: a bending area corresponding to an area at which the displaydevice is bent, and a first area and a second area which is spaced apartfrom the first area by the bending area; a display element unit which iscontrolled to display an image, the display element unit disposed on theflexible substrate in the first area of the flexible substrate; and abuffer member disposed on the flexible substrate in the bending area ofthe flexible substrate, wherein the buffer member in the bending areaincludes: a first buffer member having a first maximum thickness, and asecond buffer member having a second maximum thickness which is smallerthan the first maximum thickness, and among the first buffer member andthe second member, the first buffer member disposed closer to the firstarea and the second member disposed closer to the second area.
 2. Thedisplay device of claim 1, further comprising on a same side of theflexible substrate which is opposite to that on which the displayelement unit is disposed: a first supporting member coupled to the firstarea of the flexible substrate; and a second supporting member coupledto the second area of the flexible substrate, a first inner side of thefirst supporting member facing a second inner side of the secondsupporting member, wherein the flexible substrate bent at the bendingarea disposes along a thickness direction of the display device: thesecond supporting member overlapping the first supporting member, thefirst inner side of the first supporting member corresponding to aborder between the first area of the flexible substrate and the firstbuffer member, and the second inner side of the second supporting membercorresponding to a border between the second area of the flexiblesubstrate and the second buffer member.
 3. The display device of claim2, wherein the first buffer member is in contact with the first innerside of the first supporting member, the second buffer member is incontact with the second inner side of the second supporting member, anda thickness of a portion of the first buffer member which is directlyadjacent to and in contact with the first inner side of the firstsupporting member is greater than a thickness of a portion of the secondbuffer member which is directly adjacent to and in contact with thesecond inner side of the second supporting member.
 4. The display deviceof claim 3, wherein the first supporting member, the first buffermember, the second buffer member and the second supporting memberinclude a same material and form one integral body with one another. 5.The display device of claim 4, wherein the first and second buffermembers further include a moisture permeation preventing material, andin the bending area: the first buffer member covers a portion of theflexible substrate directly adjacent to the first inner side of thefirst supporting member, and the second buffer member covers a portionof the flexible substrate directly adjacent to the second inner side ofthe second supporting member.
 6. The display device of claim 5, whereineach of the first and second supporting members are thicker than each ofthe first and second buffer members.
 7. The display device of claim 5,wherein the flexible substrate bent at the bending area furtherdisposes: the first buffer member at a bent end of the display device,and a bottom surface of the first supporting member facing a top surfaceof the second supporting member along the thickness direction of thedisplay device, and the first buffer member extends from the bent end ofthe display device to dispose a first extension member thereofoverlapping the bottom surface of the first supporting member along thethickness direction of the display device.
 8. The display device ofclaim 7, wherein the first maximum thickness of the first buffer memberextending to define the first extension member is greater than athickness of the first supporting member.
 9. The display device of claim8, wherein the flexible substrate bent at the bending area furtherdisposes the first extension member further overlapping the top surfaceof the second supporting member along the thickness direction of thedisplay device.
 10. The display device of claim 6, further comprising:on a same side of the flexible substrate on which the display elementunit is disposed, a driving member which controls the display elementunit to display the image, the driving member disposed in the secondarea of the flexible substrate; and a circuit board which provides acontrol signal to the driving member, the circuit board connected to theflexible substrate at the second area thereof to be spaced apart fromthe driving member in the second area.
 11. The display device of claim2, further comprising on a same side of the flexible substrate on whichthe display element unit is disposed, a third buffer member disposed inthe first and second areas of the flexible substrate, the third buffermember facing the first and second buffer members in the bending area ofthe flexible substrate.
 12. The display device of claim 11, wherein athickness of the third buffer member is smaller than each of the firstand second maximum thicknesses of the first and second buffer members,and a material of the third buffer member differs from materials of thefirst and second buffer members.
 13. A display device comprising: aflexible substrate including: a bending area corresponding to an area atwhich the display device is bent, and a first area and a second areawhich is spaced apart from the first area by the bending area; a displayelement unit which is controlled to display an image, the displayelement unit disposed on the flexible substrate in the first area of theflexible substrate; a buffer member disposed on the flexible substratein the bending area of the flexible substrate, the buffer member in thebending area including: a first buffer member having a first maximumthickness, and a second buffer member having a second maximum thicknesswhich is smaller than the first maximum thickness, and among the firstbuffer member and the second member, the first buffer member disposedcloser to the first area and the second member disposed closer to thesecond area; and on a same side of the flexible substrate which isopposite to that on which the display element unit is disposed: a firstsupporting member coupled to the first area of the flexible substrate,the first supporting member including a first inner side closest to thebending area being curved to have a first curvature; and a secondsupporting member coupled to the second area of the flexible substrate,the second supporting member including a second inner side closest tothe bending area, wherein the flexible substrate bent at the bendingarea disposes along a thickness direction of the display device: thesecond supporting member overlapping the first supporting member, andthe curved first inner side of the first supporting member protrudingtoward the first buffer member.
 14. The display device of claim 13,wherein the first buffer member is in contact with the curved firstinner side of the first supporting member, the second buffer member isin contact with the second inner side of the second supporting member,and a thickness of a portion of the first buffer member which isdirectly adjacent to and in contact with the curved first inner side isgreater than a thickness of a portion of the second buffer member whichis directly adjacent to and in contact with the second inner side. 15.The display device of claim 14, wherein the first supporting member, thefirst buffer member, the second buffer member and the second supportingmember include a same material and form one integral body with oneanother.
 16. The display device of claim 15, wherein the first andsecond buffer members further include a moisture permeation preventingmaterial, and in the bending area: the first buffer member covers aportion of the flexible substrate directly adjacent to the curved firstinner side, and the second buffer member covers a portion of theflexible substrate directly adjacent to the second inner side.
 17. Thedisplay device of claim 16, wherein each of the first and secondsupporting members are thicker than each of the first and second buffermembers.
 18. The display device of claim 16, wherein the flexiblesubstrate bent at the bending area further disposes: the first buffermember at a bent end of the display device, and a bottom surface of thefirst supporting member facing a top surface of the second supportingmember along the thickness direction of the display device, the firstbuffer member extends from the bent end of the display device to disposea first extension member thereof overlapping both the bottom surface ofthe first supporting member and the top surface of the second supportingmember along the thickness direction of the display device, and thefirst maximum thickness of the first buffer member extending to definethe first extension member is greater than a thickness of the firstsupporting member.
 19. The display device of claim 13, furthercomprising on a same side of the flexible substrate on which the displayelement unit is disposed, a third buffer member disposed in the firstand second areas of the flexible substrate, the third buffer memberfacing the first and second buffer members in the bending area of theflexible substrate.
 20. The display device of claim 19, wherein athickness of the third buffer member is smaller than each of the firstand second maximum thicknesses of the first and second buffer members,and a material of the third buffer member differs from materials of thefirst and second buffer members.